How do you read a file line by line using a generator-like approach (e.g., yield return)?

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ICSM Computer · Answer

You can create a generator-like method using yield return to
read a file line by line. This is memory-efficient, especially for large files, because it reads one line at a time and doesn’t load the whole file into memory.
Example: Generator-style file reader
using System;
using System.Collections.Generic;
using System.IO;
class Program
{
    static void Main()
    {
        string path = @"C:\example.txt";
        foreach (var line in ReadLines(path))
        {
            Console.WriteLine(line);
        }
    }
    static IEnumerableandlt;stringandgt; ReadLines(string filePath)
    {
        using (var reader = new StreamReader(filePath))
        {
            string? line;
            while ((line = reader.ReadLine()) != null)
            {
                yield return line;
            }
        }
    }
}
Why use yield return here?
Defers execution: lines are read only when needed.Saves memory: no need to store all lines in a list or array.Makes the code composable with LINQ or foreach.
You can combine this with LINQ filters like:
var longLines = ReadLines("file.txt").Where(l =andgt; l.Length andgt; 80);
and

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How do you read a file line by line using a generator-like approach (e.g., yield return)?

ICSM Computer

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1 Answers

Example: Generator-style file reader

Why use `yield return` here?

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